(1) Field of the Invention
The present invention relates to an optical disc which stores multimedia data, a reproduction apparatus, and a reproduction method for reproducing such an optical disc; among them all, especially, to improving reproduction function in the interactive application.
(2) Description of the Related Art
Laser discs and video CDs are well known as optical information storage media and the reproduction apparatus for audio information and moving picture information.
Laser discs are optical discs with a diameter of about 30 cm storing analogue moving picture data of about an hour. They have been often utilized as storage media for movies and music videos. However, their size is not necessarily optimal in terms of transportation or storage, there has been an increasing demand for more compact storage media.
A video CD was realized by tailoring an audio compact disc as follows: a large amount of moving picture images were stored onto the compact disc with a diameter of 12 cm by MPEG (Moving Picture Expert Group) system. Even though, a compact disc size was realized, resolution of the moving pictures was only about 352*240.
Interactive Application
Recently, there is an increasing demand for new storage media capable of storing high-quality movie applications and also can be used in the field of "interactive application". Here, the "interactive application" has a plurality of reproduction routes and allows the user to control the direction that the application takes. Some of the examples are: an aerobics software for self-exercise; and a guide video of an overseas travel. Among them all, what is notable is that certain applications which are called "interactive movies" have been developed, which can be distinguished from the conventional movies for the interactive functions. In interactive movies, a plurality of stories are stored in parallel. Users determine the direction in the course of the story at times so that they can get the feel of reality and excitement. Here is an example of a story about a dragon and a warrior. A dragon suddenly appears in front of the warrior and a menu is displayed as follow. Option 1: Get Away. Option 2: Fight. In this way, the direction of the story is determined. Reproduction of the story keeps going, branching to the screen images which corresponds to the user's option.
Control of the Interactive Application
A conventional interactive application in the case of video CD can be explained as follows by means of FIGS. 1-3. Here is an example of a multistory-detective story (multi-story means that there are several possible direction of the story).
FIG. 1 shows moving pictures 1-5 of the detective story, which are arranged according to the order of reproduction. In moving picture 1, a detective enters a room. In moving picture 2, a pen and glasses on a desk is zoomed in for close-ups. In moving picture 3, a menu is displayed, asking the user to select either "1: glasses" and "2: a pen". In moving picture 4, glasses are zoomed in for close-ups according to the selection of "1: glasses". In moving picture 5, a pen is zoomed in for close-ups according to the selection of "2: a pen".
FIG. 2 is an example showing how the respective digital data of moving picturers 1-5 is stored on the video CD. Aside from the digital data, the video CD stores a plurality of reproduction route data which controls the order of reproduction of moving pictures 1-5. Digital data for one moving picture is stored in a series of areas. However, the respective digital data should not necessarily be stored in a series of areas. They can be stored on different areas of a disc as shown in FIG. 2.
FIG. 3 shows a plurality of reproduction route data stored on the video CD. There are two types of reproduction route data: one is giving reproduction order to a plurality of moving picture data; and the other is to switch branch destination as the reproduction proceeds.
The former type is called a "play list", in which the reproduction order of the moving pictures is designated. Also, the play list includes a piece of link information which designates the next reproduction route after the reproduction of the designated moving picture ends.
The latter type is called a "selection list". The selection list includes a plurality of reproduction routes as branch target candidates and a menu address. The menu address is a record address for a menu image that provides a plurality of branch targets. The menu image includes a plurality of items whose identification numbers correspond to identifiers of reproduction routes as the branch targets.
In FIG. 3, reproduction route data 1, 3, and 4 are play lists, and reproduction route data 2 is a selection list. The identification number of each menu item corresponds to the numeral key on the remote control panel. When the user presses a numeral key, branch occurs to the corresponding destination.
How the video CD in FIG. 2 is reproduced by its reproduction apparatus can be explained as follows.
When designated to start the reproduction, the reproduction apparatus reads the leading reproduction route data 1 from the optical disc, and stores it into an internal memory. According to the reproduction order of the moving picture designated by the reproduction route data 1, the reproduction apparatus determines the moving picture to be reproduced. After that, the reproduction apparatus moves a pickup to the position designated by the record address of the moving picture, and reads the digital data of the moving picture from the optical disc. The reproduction apparatus converts the digital data into a picture output signal and an audio output signal through a certain signal process, then outputs the signals to the display end speaker.
After the above processing, the scene of moving picture 1 is reproduced for a few seconds: a detective is entering a room in which a desk is placed. When the reproduction of moving picture 1 ends, reproduction of moving picture 2 starts. The desk is zoomed in for close-ups and the pen and glasses are displayed for a few seconds. When all motion pictures stored in the reproduction route data are reproduced, by referring to the link information of reproduction route data 1, the reproduction apparatus reads the next reproduction route data through the pickup. The reproduction apparatus, then, discards the reproduction route 1 and optically reads the next reproduction data into the internal memory. In the case of the present example, instead of the reproduction route date 1, the reproduction route data 2 is stored into the memory. In the present example, as the newly stored reproduction route data 2 is a selection list, a menu which displays a plurality of branch destinations is displayed. In this case, moving picture 3 is displayed, allowing users to select "1: glasses" or "2: pen".
When the user presses a numeral key on a remote controller corresponding to the item in the menu, the reproduction apparatus determines reproduction route data which is the branch target corresponding to the numeral. After that, the reproduction apparatus discards the reproduction route 2 and optically reads the determined reproduction data into the internal memory. In the present example, the reproduction route data 3 is read into a memory if the user selects item "1;"; and reproduction route data 4 if the user selects item "2". The reproduction apparatus continues the reproduction according to the new reproduction route data stored in the memory. If the reproduction route data 3 is stored in the memory, moving picture 4, an image of close-up glasses, is reproduced. If the reproduction route data 4 is stored in the memory, moving picture 5, an image of close-up pen, is reproduced.
When the reproduction apparatus continues the above mentioned operations to the optical disc, moving pictures are reproduced, with the route being changed according to the user's selection of the menu item. As the user can control the direction of the interactive software in a various way, he/she can get the feel of being the detective in the story.
The Task That the Present Invention is going to Solve
However, the interactive application mentioned above has the following shortcomings.
(1) Response in Interaction
In order to realize a branch of a video CD, the optical pickup alternatively has to read the moving pictures and the reproduction route data: e.g. moving picture 2, reproduction route data 2, moving picture 3, reproduction route data 3 or 4, moving picture 4 or 5. Switching the readout of the moving picture and reproduction route data entails a seek operation of the pickup, which causes interruption in the course of reproduction of the program. Especially, if the branch should occur many times, the response of the interactive reproduction deteriorates greatly, which makes the interactive application less appealing to the user.
As mentioned above, it has been difficult to realize a responsive interactive application so that a smooth reproduction of the program is kept going.
(2) A Menu
If the user does not designate the selection item on the menu screen (branch point of the reproduction), it creates a pause in the course of reproduction. In the case of the foregoing story of the dragon and the sword, the moment the dragon appears above the horizon, a menu of "Get Away" and "Fight" is displayed. Here, if the user has some hesitation to determine which course to take, the reproduction is paused. Like this, according to the conventional interactive software, normal reproduction was not realized unless the user devoted to the pursuit of the story or he/she immediately selected the direction of the story at the branch point.